How do I pass a Dictionary as a parameter to an ActionResult method from jQuery/Ajax?

Question

I'm using jQuery to make an Ajax call using an Http Post in ASP.NET MVC. I would like to be able to pass a Dictionary of values.

The closest thing I could think of was to pass in a multi-dimensional array of strings, but the result that actually gets passed to the ActionResult method is a single dimensional string array containing a string concatenation of the "key/value" pair.

For instance the first item in the below "values" array contains the below value:

"id,200"

Here's an example of my ActionResult method:

public ActionResult AddItems(string[] values)
{
    // do something
}

Here's an example of how I'm calling the method from jQuery:

$.post("/Controller/AddItems",
    {
        values: [
            ["id", "200"],
            ["FirstName", "Chris"],
            ["DynamicItem1", "Some Value"],
            ["DynamicItem2", "Some Other Value"]
        ]
    },
    function(data) { },
    "json");

Does anyone know how to pass a Dictionary object from jQuery to the ActionResult method instead of an Array?

I would really like to define my ActionResult like this:

public ActionResult AddItems(Dictionary<string, object> values)
{
    // do something
}

Any suggestions?

UPDATE: I tried passing in a comma within the value and it basically just makes it impossible to actually parse the key/value pair using string parsing.

Pass this:

values: [
    ["id", "200,300"],
    ["FirstName", "Chris"]
]

results in this:

values[0] = "id,200,300";
values[1] = "FirstName,Chris";

Answer 1

I think you're right J.W. Javascript doesn't understand the model I don't think.

I think you'll probably need to pass the members individualy.

Answer 2

It's possible with custom model binders or filters. Behind the scenes - you will have to do it manually anyway (Request.Form, parse strings, create dictionary tralala), but at least - your controller will be clean and code will be reusable for another actions.

Answer 3

I don't think it's possible to pass in a Dictionary from jQuery/Ajax to an ActionResult method via an Http Post. One thing I figured out that seems to be the easiest to work with is to pass in a JSON object and then parse that out into a Dictionary.

Here's the modified version of of the above calling "$.post" from jQuery that sends JSON as a pseudo-Dictionary:

$.post("/Controller/AddItems",
    {
        values: Sys.Serialization.JavaScriptSerializer.serialize(
                {
                    id: 200,
                    "name": "Chris"
                }
            )
    },
    function(data) { },
    "json");

The "Sys.Serialization.JavaScriptSerializer.serialize" function is a method of the ASP.NET AJAX JavaScript library.

Here's the modified version of the above ActionResult method:

public ActionResult AddItems(Dictionary<string, object> values)
{
    // Must Reference "System.Web.Extensions" in order to use the JavaScriptSerializer
    var json = new System.Web.Script.Serialization.JavaScriptSerializer();
    var data = json.Deserialize<Dictionary<string, string>>(routeValues);

    // do something
}

I think this makes it much easier to Unit Test by passing JSON, instead of using the Form Collection to send/retrieve the collection of key/value pairs. Also, it's easier to get working than figuring out how to build a custom IModelBinder, and a custom IModelBinder might cause issues with other ActionResult methods when this is the only one I need to do this.

Answer 4

DefaultModelBinder is able to bind your POST to array or dictionary. For example:

for arrays:

public ActionResult AddItems(string[] values)

$.post("/Controller/AddItems", { values: "values[0]=200&values[1]=300" },
    function(data) { }, "json");

or:

$.post("/Controller/AddItems", { values: "values=200&values=300" },
    function(data) { }, "json");

for dictionaries:

public ActionResult AddItems(Dictionary<string, object> values)

$.post("/Controller/AddItems", {
    values: "values[0].Key=value0&values[0].Value=200&values[1].Key=value1&values[1].Value=300" }, function(data) { }, "json");

UPDATED:

If your values are in HTML inputs then in jQuery you can do something like this:

var postData = $('input#id1, input#id2, ..., input#idN").serialize();
// or
var postData = $('input.classOfYourInputs").serialize();

$.post("/Controller/AddItems", { values: postData }, function(data) { }, "json");

UPDATED:

Also check this: Scott Hanselman's ComputerZen.com - ASP.NET Wire Format for Model Binding to Arrays, Lists, Collections, Dictionaries

Answer 5

At last I figured it out!! Thanks for the suggestions everyone! I finally figured out the best solution is to pass JSON via the Http Post and use a custom ModelBinder to convert the JSON to a Dictionary. One thing I did in my solution is created a JsonDictionary object that inherits from Dictionary so that I can attach the custom ModelBinder to the JsonDictionary type, and it wont cause any conflicts in the future if I use Dictionary as a ActionResult parameter later on for a different purpose than JSON.

Here's the final ActionResult method:

public ActionResult AddItems([Bind(Include="values")] JsonDictionary values)
{
    // do something
}

And the jQuery "$.post" call:

$.post("/Controller/AddItems",
{
    values: Sys.Serialization.JavaScriptSerializer.serialize(
            {
                id: 200,
                "name": "Chris"
            }
        )
},
function(data) { },
"json");

Then the JsonDictionaryModelBinder needs to be registered, I added this to the Application_Start method within the Global.asax.cs:

protected void Application_Start()
{
    ModelBinders.Binders.Add(typeof(JsonDictionary), new JsonDictionaryModelBinder());
}

And, finally here's the JsonDictionaryModelBinder object and JsonDictionary object I created:

public class JsonDictionary : Dictionary<string, object>
{
    public JsonDictionary() { }

    public void Add(JsonDictionary jsonDictionary)
    {
        if (jsonDictionary != null)
        {
            foreach (var k in jsonDictionary.Keys)
            {
                this.Add(k, jsonDictionary[k]);
            }
        }
    }
}

public class JsonDictionaryModelBinder : IModelBinder
{
    #region IModelBinder Members

    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        if (bindingContext.Model == null) { bindingContext.Model = new JsonDictionary(); }
        var model = bindingContext.Model as JsonDictionary;

        if (bindingContext.ModelType == typeof(JsonDictionary))
        {
            // Deserialize each form/querystring item specified in the "includeProperties"
            // parameter that was passed to the "UpdateModel" method call

            // Check/Add Form Collection
            this.addRequestValues(
                model,
                controllerContext.RequestContext.HttpContext.Request.Form,
                controllerContext, bindingContext);

            // Check/Add QueryString Collection
            this.addRequestValues(
                model,
                controllerContext.RequestContext.HttpContext.Request.QueryString,
                controllerContext, bindingContext);
        }

        return model;
    }

    #endregion

    private void addRequestValues(JsonDictionary model, NameValueCollection nameValueCollection, ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        foreach (string key in nameValueCollection.Keys)
        {
            if (bindingContext.PropertyFilter(key))
            {
                var jsonText = nameValueCollection[key];
                var newModel = deserializeJson(jsonText);
                // Add the new JSON key/value pairs to the Model
                model.Add(newModel);
            }
        }
    }

    private JsonDictionary deserializeJson(string json)
    {
        // Must Reference "System.Web.Extensions" in order to use the JavaScriptSerializer
        var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
        return serializer.Deserialize<JsonDictionary>(json);
    }
}